Since, maximum frequency is `f_(1)=18`, so its modal class (4000-5000)
`:.` (Lower modal class) `l=4000,f_(m)=18,f_(2)=9, ` (class width ) h=1000
`"Mode"=l+((f_(i)-f_(0))/(2f_(1)-f_(0)-f_(2)))xxh=4000+((18-4)/(36-4-9))xx1000`
`=4000+(14000)/(23)`
`=4000+608.7` runs